126 TRANSACTIONS-PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
is figured, from a specimen in the collection of the late Lord Kin- 
naird, while Sir William Dawson refers to cases of the same kind. 
But the fact remains, that, if in determining fossil plants, this dictum 
in regard to organic union of stem, branch, and fruit, were to be acted 
upon, but few plants of the Old Red Sandstone, or of any other for¬ 
mation, would prove eligible. 
We are painfully familiar with the fragmentary condition in which 
the plants of the Old Red Sandstone occur, and cases of organic 
union are undoubtedly but few and far between. The palseobotanist, 
therefore, in dealing with the imperfect material at his command, 
more frequently finds it necessary to break the rules'' than to 
observe them. An example of this occurs in a paper by Mr. Kidston 
“On Arthrostigma,” ^ which states, “That the Perthshire specimens 
must be identified as Arthrostigma gracile (Dawson),” though the 
evidence upon which this opinion is based is comprised in a few 
fragments of somewhat obscure stems, devoid of branches or fruit. 
Again, we find an interesting paper by this author “On the occurrence 
of the genus Equisetum in the Yorkshire Coal Measures,”! in which 
a representative cone i inch in length by inch in breadth is figured, 
and “ Beyond evidence gained from an examination of the surface of 
the fossil (cone) there is none.” No stems, branches, or seed occur. 
We may therefore search in vain for evidence of “ organic union ” 
in this case, none such occurring in the Carboniferous formation of 
England. 
The paper is an able one, and we are far from questioning the 
conclusion arrived at. Yet it will be generally conceded that had a 
few fragments of branches or stems of Equisetum been discovered in 
association with this cone (or cones), the case would have been 
materially strengthened. 
Parka decipie 7 is^ on the other hand, occupies a much stronger 
position. Perhaps Parka —possessing sporocarp, and sporangia of 
rhizocarpian structure—could better afford to dispense with stems 
and leaves than even Equisetimi. The rhizocarpian form, however, 
of these, and their invariable presence in the same beds in which the 
fruit-clusters of Parka occur, irresistibly point to the same origin. 
In conclusion, the excellent work accomplished by Dawson and 
Penhallow has undoubtedly advanced the Parka question beyond 
the reach of conjectural opinion. And we are in no small measure 
indebted to the veteran geologist, who has so ably solved the problem 
of Parka decipiens^ the “ deceiving ” nature of which has proved (for 
so many years) a stumbling-block in the way of leading geologists of 
our time. 
* Trans. Roy. P. Soc. Edinburgh, 1893. 
tThe Annls. and Mag. N. History, 1892, pp. 140, 141. 
